C# - Mapping A Filename To Paths On A Server?

I have a problem with my code. My code is using the fileupload control to browse for a filename when you add a filename it processes it and the code runs fine on when it lives on local host, but when I put the code on our prodution server it cannot find the filenames listed by user.

For example if I use the upload control to browse to B:MISCH IntiveRPTTOFL_3.csv and the code lives on my localhost which know what that file path means it works, but if the code is moved to a production server it may or maynot know what B:/ is or B:/ maybe mapped to something else. Even if I am browsing to a file on my C drive it will work on if the code is on the machine that the C drive is on, but it will not work if the code is on another machine because obviously that file wouldnt be on that C drive.

Private Function CSV2DataTable(ByVal filename As String) As DataTable

Using MyReader As New _
Microsoft.VisualBasic.FileIO.TextFieldParser(filename)
MyReader.TextFieldType = FileIO.FieldType.Delimited

What can I do in asp.net to make the filename work correctly?

Ok lets say I get the filename and save it as so

FileUploadControl.SaveAs(Server.MapPath("~/") + filename);

now I want to pass the filename to the function above for processing. Do I pass Server.MapPath("~/") + filename as the filename? Also when I am done what do I do to delete the file from the server?